Why Sleep Quality Indicators Are Useful (and When to Ignore Them)
Sleep tracking apps promise to improve your sleep quality through data analysis. But what happens when the pursuit of perfect results keeps you up at night? For a growing number of people, the Apple Watch, Oura Ring, or any other device purported to improve sleep quality may actually have the opposite effect. Here’s what you need to know about how sleep quality metrics actually work and what you can do to get the most out of your sleep tracker.
The Benefits (and Accuracy) of Sleep Tracking
Sleep is fundamental to virtually every aspect of health, including “improving mood, heart health, and cognitive function,” says Dr. Rebecca Robbins , associate professor of sleep medicine at Harvard Medical School and a sleep research fellow at Brigham and Women’s Hospital. On the other hand, chronic sleep deprivation is associated with an increased risk of cardiovascular disease, metabolic disorders, weakened immune response, and mood disorders.
However, for decades, people have had a surprisingly poor understanding of how much time they actually sleep. Self-reporting is notoriously unreliable; we tend to round up, confuse time spent in bed with time spent asleep, and completely forget about nighttime awakenings. “In recent years, consumer sleep tracking devices have begun to close this gap, significantly improving the accuracy and reliability of data while providing more information from home,” says Robbins. The Oura Ring and Whoop Band dominate the market, but watches like Fitbit or Apple Watch are also suitable.
According to Robbins, wearable devices (such as wristbands or rings) are equipped with a variety of sensors with increasing accuracy: a temperature sensor, an accelerometer for measuring movement, light sensors, and photoplethysmography (PPG) technology. (PPG uses pulses of light to detect blood flow under the skin, allowing the device to calculate heart rate and estimate blood oxygen saturation.)
Your device tracks how long you apparently slept and makes an estimate of how much of that time was spent in light sleep, deep sleep, and rapid eye movement (REM) sleep. It then converts this into a single aggregate score. This is a useful metric, but it’s important to remember that it’s an estimate, and each company has its own scoring system .
There’s also the question of what “quality sleep” even means. The clinical definition relies on sufficient duration (most adults need seven to nine hours), sufficient continuity, proper distribution of sleep stages, and, crucially, how you feel upon waking and throughout the day. This last part is ultimately a subjective experience—in other words, something no wearable device can measure. Someone who wakes up after eight hours of uninterrupted sleep feeling sluggish and unrefreshed isn’t having quality sleep, regardless of what their sleep app says. Conversely, someone who wakes up refreshed and energized after a night where their sleep tracker rated them a 65 should probably trust their body more than an algorithm.
This is why sleep quality ratings can’t be truly “accurate.” While all the data that influences the rating (such as heart rate) may be accurate, it’s important to understand that the rating itself is a fictitious number. Different companies use different definitions of “good” sleep, which vary depending on the device. For example, Oura and Apple provide ratings from 0 to 100, but while Oura defines a score of 70-84 as “good,” Apple defines a range of 61-80 as “fair.” These ratings cannot be considered clinically accurate.
However, for most people, clinical accuracy isn’t a primary concern. If the goal is to get behavioral feedback, your smartwatch or sleep tracker is an excellent tool.
Wearable devices can be useful in facilitating habit change.
Ideally, sleep tracking works not like a medical test you pass or fail, but rather as a way to identify patterns over time. You might begin to notice the gradual impact of a late-night glass of wine on your deep sleep percentage, or how your resting heart rate increases after three nights of going to bed earlier than usual, or perhaps the distinct difference a consistent sleep routine makes over several weeks.
“People are highly motivated by their performance,” says Robbins. “Wearables can foster intrinsic motivation to change behavior by providing daily feedback.” In other words, your performance (good or bad) can prompt you to reflect on your actions: What did I do yesterday? What can I do differently tonight?
The key here is that you don’t need to “optimize” every stage of your sleep structure to benefit from this kind of tracking. “The most effective use of this data is the ability to track your progress over time,” says Robbins. Instead of obsessing over your results every night, you should focus on whether you’re moving in the right direction.
Some of these devices, like Oura Advisor , also incorporate a coaching element. In these cases, wearables can go beyond passive monitoring and actively identify inconsistencies, for example, by alerting me to irregular bedtimes (which, over time, disrupts the body’s circadian rhythm). I can imagine not truly realizing that my weekend schedule is negatively impacting my weekday sleep, and such an alert would help me make the necessary changes. These devices are particularly effective “for people who are far from healthy sleep patterns, such as those with irregular schedules or sleep deprivation, because they provide behavioral feedback and personalized recommendations,” says Robbins.
For people who respond well to positive reinforcement, the gamification built into many platforms—uninterrupted sleep counters, badges—can also help them resist the small mistakes that degrade sleep quality. Of course, gamification has a downside . What happens when your obsession with sleep is the very thing that keeps you up at night?
Orthosomnia and sleep-tracking anxiety
Not everyone responds to sleep quality data with motivation. For some, daily sleep data can actually trigger a feeling of dread.
Researchers have given this phenomenon a name: orthosomnia. This term, coined in a 2017 article published in the Journal of Clinical Sleep Medicine , describes an obsession with achieving ideal sleep patterns that paradoxically worsens sleep quality. (It should be clarified that this term is not actually a formal clinical diagnosis.)
“This phenomenon typically affects people already prone to grade anxiety, where receiving daily feedback can trigger a spiral of rumination and worry that ultimately limits their ability to sleep well the following night,” says Robbins. You sleep poorly, your performance reflects this, your anxiety about the performance intensifies, this anxiety interferes with your sleep the following night, which leads to another poor performance, and so on. The stress of receiving poor grades creates a snowball effect, leading to more and more poor performance.
The situation is exacerbated by another problem I constantly see in the wellness space: information overload . When you’re shown sleep stages, breathing rate, heart rate variability, skin temperature fluctuations, activity levels, alertness indicators, and more, it’s natural to feel overwhelmed. Instead, as Robbins says, “The most useful metrics for most people are often the simplest ones, like total sleep amount and a score indicating whether the night was a success.”
How to Actually Track Your Sleep
If you’re going to use a sleep tracker, the goal is to track overall patterns rather than focusing on nightly sleep patterns. Sleep is inherently variable, and even healthy people have bad nights. What’s important is whether your weekly average is moving in the right direction. Use monthly data, not daily data, as a primary benchmark.
Second, identify metrics that are truly useful for you. If you know your deep sleep is significantly impaired after drinking alcohol, that’s helpful. If you’re anxiously updating your heart rate variability data without knowing what to do with it, you’re likely stressed for no apparent reason. Robbins recommends keeping it simple: total sleep time and an overall assessment of how well you spent the night are usually sufficient for most people. Another metric worth tracking is whether you feel sluggish during the day. This may be subjective, but it’s a clear indicator of whether you’re getting enough quality sleep.
Finally, know when to put the device down. “If tracking is causing you anxiety, take a break from using the device or avoid looking at the data,” says Robbins. Perhaps taking a week or two off from using a sleep app or simply avoiding checking the data in the morning will help break the cycle of anxiety and allow you to approach bedtime with less stress.
Some tips for better sleep
If you find yourself relying too much on sleep quality metrics in pursuit of more restful sleep, try other methods. Sleep hygiene principles are considered classics for good reason.
Avoid using screens before bed.
We all know this already, but it’s still a hard habit to break. Blue light emitted by phones and laptops suppresses melatonin production ; in addition to light, the mental strain of scrolling through news feeds or replying to messages keeps the nervous system activated, making it difficult to fall asleep.
Replace screens with something truly calming.
Instead of simply eliminating bad habits, consider adding one or two new ones. Robbins suggests “calming activities like reading a book, taking a warm shower, or practicing mindfulness.”
Turn on active relaxation.
Don’t wait until you feel tired and hope sleep follows. Instead, try to consciously incorporate relaxation techniques into your daily routine. Breathing exercises , gentle stretching, or perhaps a simple body scan meditation can all work wonders.
Stick to your sleep schedule.
Consistency in sleep and wake times is one of the most important factors determining sleep quality, as it ensures the smooth functioning of the circadian rhythm.
Be honest with yourself about stimulants.
This is a difficult question for me, but drinking coffee at 3 PM can significantly disrupt sleep that begins at 10 PM. Alcohol, on the other hand, may initially speed up falling asleep, but in the second half of the night, it disrupts sleep.